Optical contouring is a full field, non-contact
technique capable of determining shape and deformation data
from 3-D surfaces. The data, which are obtained from the
optical contouring system, represent the surface geometry
at evenly sampled points. The main objective of this thesis
is to report some advances achieved by the author in the
optical contouring field. Conditions for the design and
construction of optical systems to measure object
topography and deformation using the same hardware, as well
as the optical working methodology and system parameters,
are analysed. The conventional in-plane and out-of-plane optical
setups for displacement sensitive ESP I systems are employed
to contour. The contour maps are obtained by giving small
displacements to optical fibres carrying the object and
reference beam illumination. A rigorous mathematical
treatment of shape contours generated by ESPI is given. It
is experimentally verified that the fringe patterns
produced are identical to projected fringe contours, and
may be analysed in the same way. Then, practical systems
which combine deformation and shape measurement in both
in-plane and out-of-plane ESPI configuration are
demonstrated. Comparison is made with shape measurement using two
fringe projection moire techniques. The first moire
technique uses electronic demodulation to obtain the
contour maps. This technique encodes and analyses moire
contours by using an electronic system similar to that used
for Electronic Speckle Pattern Interferometry (ESPI). Hence
automatic fringe detection and contour measurement is
possible. The Talbot effect, where the self imaging of a periodic
object is used as second moire technique. The Talbot image
of a linear grating is imaged on the target surface. The
grating lines are deformed according to the surface shape.
Viewing this deformed grating image through a second
reference grating, generates contour maps. A novel on-axis
sensor which directly measures distance as a direct colour
mapping is introduced.
It is emphasized that all the techniques researched here
can be extended to be applied as industrial tools for
surface inspection or quality control. Phase-shift
measurement and digital image processing are employed for
data reduction.

Description:

A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.